none of mario batali's restaurants have an actual dress code. in fact, because Mario always wears shorts, he believes that the patrons at his restaurants should also be able to wear shorts. i don't know that I would feel entirely comfortable in shorts at Del Posto, but that example is more just to show that there is no strict dress code there.

as for recs... most of the dishes there are excellent. I have always liked the tuna as well as any of the pastas. Save room for dessert because its probably the best part!